The invention relates to a method and/or an appliance for determining the load on an internal combustion engine of a vehical, in accordance with the respective features of the preamble to the independent patent claims.
Methods and appliances for determining the load on internal combustion engines of vehicles are known. Thus, in a known method, the air mass flow is determined from a characteristic diagram from the engine speed and the position of a control element (throttle butterfly angle) which determines the power of the internal combustion engine, the load being calculated from the air mass flow read from the characteristic diagram, this air mass flow being used for further open-chain/closed-loop control of the internal combustion engine.
In addition, there are similarly operating methods in which, as the operating parameter of the internal combustion engine, an intake pipe pressure is recorded or the air mass flow may also be directly recorded, in addition to the engine speed. These two methods, which take account of the intake pipe pressure or the air mass flow as the operating parameter, have the disadvantage that these operating parameters have to be provided with their own sensor, whichxe2x80x94especially in the mass production of internal combustion enginesxe2x80x94represents a substantial cost factor, particularly since these sensors are very expensive. In addition, these additional sensors demand a further assembly outlay and, in addition, contain a fault source because the sensors can fail.
Although, in contrast, the method mentioned first, which takes account of the engine speed and the throttle butterfly angle, is indeed favorable from the cost point of view because it dispenses with a further sensor, it is also associated with inaccuracy disadvantages because it involves an indirect measurement method, in that the association of the measured engine speed and the measured throttle butterfly angle with the air mass flow read from the characteristic diagram is extremely susceptible to error, in that it is only possible to record the load in a very inaccurate, transient manner and in that no account is taken of atmospheric conditions because the air mass flow is determined and stored as a characteristic field, which is plotted against the engine speed and the throttle butterfly angle, during a test bed investigation (test series) at certain constant atmospheric conditions only.
The invention is therefore based on the object of providing a method and an appliance for determining the load on an internal combustion engine of a vehicle, which method avoids the disadvantages described and supplies an accurate conclusion on the load on the internal combustion engine at reduced assembly and cost outlay.
The recording of at least one further parameter, which is not an operating parameter of the internal combustion engine, and subsequently taking account of it during the load determination has the advantage of correcting the values read from the characteristic diagram as a function of the operating parameters of the internal combustion engine, which values represent the load on the internal combustion engine or from which the load on the internal combustion engine can be calculated, by further parameters, such as, for example, atmospheric conditions (for example air pressure and air temperature) in order to carry out the correction rapidly and at favorable cost and to determine a very accurate value for the actual load on the internal combustion engine.
It is, furthermore, advantageous for the further parameter to be recorded by a sensor already present in the vehicle so that, in consequence, it is possible to dispense with an extra sensor for recording the further parameter. This reduces the assembly outlay, the spare parts holding and the fault susceptibility because there is at least one less sensor present which can fail. In addition, the whole of the wiring for such an extra sensor is dispensed with so that, in consequence, weight savings are also possible. The current measurement of the further parameter is transmitted to the control device via a data line, in particular a CAN bus. The sensor, which is configured as a pressure and/or temperature sensor, isxe2x80x94for examplexe2x80x94a constituent part of an air-conditioning installation for regulating the shut-off of the air-conditioning installation of the vehicle, a constituent part of a tank system for recording leaks in a tank of the vehicle or even part of a pneumatically operated central locking installation, i.e. use is made of the effect of transferring sensors present in other control devices to yet other control devices, which can then use this measurement for its own tasks.
In consequence, the method according to the invention has the additional advantages that the atmospheric conditions are present immediately on starting the internal combustion engine and the load can therefore be corrected as a function of these conditions. This is then of particular advantage should the atmospheric conditions depart substantially from the conditions on which the test bed investigation was based. Furthermore, it is not only the air mass flow read from the characteristic diagram which can be corrected as a function of the further parameters, it is also possible to correct further operating parameters (for example, more precise determination of the intake pipe pressure) and also to specify or correct specified pilot control values for the lambda control or idling control, for example.
Appliances are, furthermore, provided which can, for example, be used for carrying out the method according to the invention, to which appliances, however, the method is not limited.